Poster Presentation 36th Lorne Cancer Conference 2024

Preclinical evaluation of ACVR1 inhibitor TP0184, as a single agent and in combination with irradiation and trametinib in Diffuse Midline Gliomas. (#154)

Maria Tsoli 1 , Jie Liu 1 , Aaminah Khan 1 , Xinyi Guo 1 , Rebecca Rogers 2 , Shiva Senthil Kumar 1 2 , Elisabet Fernandez Potente 2 , Matt Biery 3 , Yura Grabovska 2 , Alan Mackay 2 , Diana Carvalho 2 , Rita Pereria 2 , Anna Burford 2 , Drenusha Sejdiu 2 , Ruth Ruddle 2 , Florian Gabel 2 , Florence Raynaud 2 , Sridevi Yadavilli 4 , Sean Mizoguchi 4 , Bavani Subramaniam 4 , Lindsey Kilburn 4 , Eugene Hwang 4 , Javad Nazarian 4 , Nicholas Vitanza 3 , Rachid Drissi 4 , David S Ziegler 1 , Chris Jones 2
  1. Children's Cancer Institute, Randwick, NSW, Australia
  2. Institute of Cancer Research, London, UK
  3. Seattle Children’s Research Institute,, Seattle, USA
  4. Children’s National Medical Center, Washington, USA

Somatic mutations in ACVR1, encoding the serine/threonine kinase ALK2, are prevalent in 20-25% of DMG-H3K27M patients. While ALK2 inhibitors (ALK2i) extend survival in ACVR1-mutant orthotopic xenografts, these inhibitors do not achieve complete tumour regression as monotherapy. To uncover novel combination strategies, an international collaborative effort combined resources to evaluate the novel ALK2i TP-0184 across a large panel of patient-derived DMG-H3K27 models in vitro, revealing IC50 values ranging from approximately 0.5 to 10 mM, irrespective of ACVR1 mutation status. Western blot analysis demonstrated the inhibition of phospho-SMAD1/5/9 and PI3K following TP-0184 treatment. Synergistic interactions were observed between TP-0184 and the MEK inhibitor trametinib in ACVR1-mutant DMG models in flow cytometric analysis for apoptosis and in vitro cytotoxicity assays. Importantly, combining TP-0184 with radiation in vitro demonstrated profound radiosensitisation effects in three ACVR1-mutant models, as corroborated by clonogenic assays and increased gH2AX levels and cleaved caspase 3 using western blotting. Animal studies determined the tolerable dosing regimen for TP-0184, either alone or in combination with trametinib, with the optimal doses established at 100 mg/kg/day for TP-0184 and 0.4 mg/kg/day for trametinib. In vivo efficacy studies using an orthotopic DMG model harbouring ACVR1 mutation revealed a moderate yet significantly enhanced median survival (61 days) with TP0184 monotherapy compared to vehicle control (56 days). Notably, combining TP-0184 with either irradiation or trametinib further extended animal survival (71 days for TP-0184/Trametinib and 79 days for TP0184/Irradiation) compared to single-agent treatments (67 days for irradiation and 59.5 days for trametinib). Ongoing in vivo studies involving additional DMG-H3K27 models across multiple laboratories are underway to assess the combination of TP-0184 with trametinib and radiation comprehensively. These findings have led to the inclusion of both TP-0184 combinatorial approaches as treatment arms in the TARGET precision-guided clinical trial for paediatric high-grade gliomas, coordinated internationally through the CONNECT consortium.